Compositions for making up and/or for caring for the skin and/or lips conventionally comprise a film-forming polymer known for improving the hold of these compositions on keratinous substances and in particular, where a lipstick is concerned, the hold of the lipstick on the lips.
However, such film-forming polymers are generally conveyed in volatile oils (it being possible for the latter to be used, for example, as polymerization solvent for the film-forming polymer) which can present feelings of discomfort on application and can be harmful to the gloss of the deposited layer of lipstick. Furthermore, the presence of this volatile oil involves constraints in terms of the preparation process, in particular for the preparation of lipsticks comprising solid fatty substances, such as waxes, having a high melting point, for which it is necessary to heat to a temperature generally greater than that of the flash point of the volatile oil.
Furthermore, these compositions comprising a volatile oil have to be packaged in a packaging in order to protect from any evaporation of the solvent (that is to say of the volatile oil) from the composition during storage. This constraint on the packaging represents an additional cost.
The documents EP 1 411 069 and EP 1 882 709 disclose cosmetic compositions comprising block polymers conveyed in a volatile oil having a flash point of less than 80° C. (such as, for example, isododecane).
These block polymers are in particular synthesized in the presence of isododecane. In point of fact, the block polymer, conveyed in a volatile oil having a flash point of less than 80° C., such as isododecane, can only be formulated with cosmetic additives not requiring a stage of heating at a temperature greater than that of the flash point of the volatile oil.
Thus, for example, the introduction of a solid fatty substance, such as a wax or a pasty fatty substance, exhibiting a flash point greater than the flash point of the volatile oil cannot be carried out; this is because it would be necessary to heat the mixture of polymer, volatile oil and solid fatty substance to a temperature greater than the flash point of the volatile solvent.
In addition, the presence of a large amount of volatile oil having a flash point of less than 80° C. is harmful to good cosmetic properties being obtained for a cosmetic composition to be applied to the lips or skin. This is because a high content (that is to say of greater than 10%) of volatile oil brings about a feeling of dryness and tightness on the lips or skin (feeling of discomfort) and a reduction in the gloss of the deposited layer formed after application of the composition to the lips or skin.